By Jessica Glenza for The Guardian. Above photo: Wealthy Americans can expect to live 15 years longer than poor peers, studies in the Lancet find. Photograph: Ariel Skelley/Getty Images/Blend Images

Health insurance system – the most expensive in the world – is worsening situation, researchers find, arguing healthcare should be treated as human right.

You can’t buy time – except, it seems, in America.

Increasing inequality means wealthy Americans can now expect to live up to 15 years longer than their poor counterparts, reports in the British medical journal the Lancet have found.

Researchers said these disparities appear to be worsened by the American health system itself, which relies on for-profit insurance companies, and is the most expensive in the world.

Their conclusion? Treat healthcare as a human right.

“Healthcare is not a commodity,” wrote US Senator Bernie Sanders in an opinion article introducing the issue of the journal, which is devoted to inequality in American healthcare. “The goal of a healthcare system should be to keep people well, not to make stockholders rich. The USA has the most expensive, bureaucratic, wasteful, and ineffective healthcare system in the world.”

Sanders, like authors of the lead report, called for single-payer health insurance or what Americans might know as “Medicare for all”, a reference to an existing public health program for older Americans.

“Making sure that every citizen has the right to childcare, healthcare, a college education, and secure retirement is not a radical idea. It is as American as apple pie,” he said.

The Lancet studies looked at how the American health system affects inequality and structural racism, and how mass incarceration and the Affordable Care Act (ACA), also known as Obamacare, have changed public health.

Among the studies’ key findings: the richest 1% live up to 15 years longer than the poorest 1%; the same gap in life expectancy widened in recent decades, making poverty a powerful indicator for death; more than one-third of low-income Americans avoid medical care because of costs (compared to 7% in Canada and 1% in the UK); the poorest fifth of Americans pay twice as much for healthcare as a share of income (6% for the poor, versus 3.2% for the rich); and life expectancy would have grown 51.1% more from 1983 to 2005 had mass incarceration not accelerated in the mid-1980s.

The poorest Americans have suffered in particular, with life expectancies falling in some groups even while medicine has advanced. For example, researchers reported that the poorest fifth of women born between 1930 and 1960 statistically lived four years less than Americans in the top fifth of the socioeconomic spectrum.

All of these health outcomes arrive in the context of widening general inequality. The share of total income going to the top 1% of earners has more than doubled since 1970, making the US more unequal than all but three developed countries: Chile, Mexico and Turkey.

At the same time, the ACA brought relief to many. The number of Americans without insurance dropped from 48.6 million in 2010 to 28.6 million in 2015. The number of Americans who struggle with medical bills dropped from 41% to 35% in 2014.

Further, accounting for current public health insurance programs, military healthcare, the portion of local and state budgets used to purchase private health insurance for workers, and subsidies to employers to buy workers health insurance, researchers believe as much as 65% of health insurance nationally is already paid for by taxpayers.

The conclusions come at a tumultuous time for American healthcare.

Donald Trump’s election threw his predecessor’s market-based health laws into question. Trump promised multiple times on the campaign trail to repeal the ACA and replace it with “something terrific”.

Insurance companies have increasingly passed costs on to consumers through “cost-sharing”, or asking Americans to pay more for doctor’s visits, prescription drugs and procedures before insurance kicks in. Sky-high prescription drug prices have prompted public outrage. And a requirement that Americans purchase insurance, even with government subsidies, was politically toxic.

Though Republicans promised for more than seven years to repeal the ACA – if they could only gain control of the federal government – once Trump took office, they offered a plan not conservative enough for conservatives, and not moderate enough for moderates. With an abysmal public approval rating of just 17%, the plan combusted weeks after it was introduced. Failure to pass the bill became a major loss for the Trump administration.

That has left a vacuum of ideas. Republicans tried and failed to resurrect a version of the hated plan this week. Progressives have expressed hope that single-payer reform could move into the forefront.

“I, like many others, was deeply concerned with Republican proposals that went down in flames,” said Dr David Himmelstein, a New York City doctor and co-founder of Physicians for a National Health Program, a group that lobbies for single-payer health reform. Himmelstein was also the author of one Lancet report, America: Equity and Equality in Health.

“It would have been tremendously damaging to large numbers of people in our country. So the defeat of that proposal was encouraging,” he said.

“It’s opened up much more room for debate about what there should be, so in that way, I think it’s an encouraging time that has perils but also opportunities.”

However, single-payer healthcare remains unpopular with American conservatives, who still control the government.

Robert Moffit, a researcher at the conservative thinktank the Heritage Foundation, argued that Americans would use healthcare willy-nilly if it were provided by the government.

“I mean look – you can save money with a single-payer system, don’t misunderstand me, but the quality and supply of medical services is going to be determined by government officials,” he said.

“You’re going to have inequalities in any state,” he said, calling it it “naive” to believe a “government-run system that is going to ultimately be highly politicized” would be better than a private one.